问题
I am checking for values in a textbox to trigger a conditional statement, but am getting error messages.
if (txtAge.Text = "49") || (txtAge.Text = "59")
{
txtNote.Text = "A valid picture ID must be submitted";
}
The error message I am getting is Cannot implicitly convert type 'string' to 'bool'
How can I resolve this?
回答1:
When you type this:
if (txtAge.Text = "49")
This basically is assigning "49" to txtAge.Text, and then returning that value as a string (equal to "49").
This is the same, essentially, as doing:
string tmp = txtAge.Text = "49";
if (tmp) { //...
However, you cannot do "if (stringExpression)", since an if statement only works on a boolean. You most likely wanted to type:
if (txtAge.Text == "49" || txtAge.Text == "59")
{
回答2:
In the if statement replace = by ==.
You're using the assignment operator instead of the equals comparison.
The syntax for the if statement is also not correct. Check if-else (C# Reference).
回答3:
you cannot use "=" to compare strings. in this case you could use txtAge.Text.comparedTo("49") == 0 and so on
回答4:
Need to use == instead of =. Former is used for comparison while the later is for assignment.
A better way is to use Equals method
if (txtAge.Text.Equals("49") || txtAge.Text.Equals("59"))
{
}
回答5:
You are missing ='s. Also, you may need another set of Brackets around the whole if statement.
来源：https://stackoverflow.com/questions/2357354/getting-error-msg-cannot-implicitly-convert-type-string-to-bool